The present invention is directed to control of fuel flow in gas-operated internal combustion engines, such as LPG and natural gas engines, and more particularly to an integrated control unit that includes a fuel inlet filter, a high-pressure fuel lock-off and a pressure regulator/vaporizer.
It is a general object of the present invention to provide a fuel control unit for gas-operated internal combustion engines in which a fuel inlet filter, a high-pressure lock-off and a fuel vaporizer/pressure regulator are integrated into a single assembly. Another and more specific object of the invention is to provide an integrated control unit of a described character that includes a device for affirmatively blocking fuel flow when the engine is not in operation. The integrated control unit of the invention has the further objective of reducing assembly time and the number of component parts that would otherwise be necessary in systems in which the several sections are provided as separate units. Furthermore, the integrated control unit of the invention has the objective of requiring a reduced amount of installation space on or associated with the engine.
An integrated fuel control unit for gas-operated internal combustion engines in accordance with a presently preferred embodiment of the invention includes a base on which a primary diaphragm is secured to define a primary fuel chamber. A primary fuel orifice is carried by the base, as is a primary control lever that is coupled to the primary diaphragm for controlling flow of fuel through the primary orifice as a function of inlet fuel pressure and engine demand. A secondary diaphragm is also secured to the base to define a secondary fuel chamber. A secondary orifice is carried between the primary and secondary chambers, and a secondary control lever is coupled to the secondary diaphragm for controlling flow of fuel through the secondary orifice as a function of engine demand. A heat exchange section in the body receives engine coolant or engine oil for heat exchange with fuel so as to heat and vaporize the fuel between the primary and secondary chambers. A high-pressure fuel lock-off is carried by the body, and includes a solenoid coil mounted on the body and a solenoid plunger within the coil for selectively closing an end of the primary orifice remote from the primary control lever. A fuel inlet filter is carried by the body for filtering fuel prior to passage to the primary orifice and the lock-off. The solenoid plunger is normally urged by fuel inlet pressure and by a plunger spring to close the primary orifice, and is withdrawn from the primary orifice against the force of the spring by energization of the solenoid coil when the engine is operating. This feature helps ensure that fuel will not flow to the engine when the coil is not energized and the engine is not operating.
In accordance with a particularly preferred embodiment of the invention, the integrated fuel control unit for gas-operated internal combustion engines includes abase in which a primary fuel orifice with on/off lock-off control is on one end and a primary chamber variable fuel control valve is on the opposite end. The high pressure fuel lock-off is carried by the body, and includes a solenoid coil mounted on the body and a solenoid plunger within the coil for selectively closing an end of the primary orifice remote from the primary control lever. A fuel inlet is carried by the body and filter housing cover for filtering fuel prior to passage to the lock-off and primary orifice. The solenoid plunger is normally urged by fuel inlet pressure and by a plunger spring to close the lock-off end of orifice and is withdrawn from the lock-off end of orifice against the force of the spring by energization of the coil when the engine is operating or when activating during start mode. This feature ensures that fuel will not flow to the engine when the coil is not energized and the engine is not operating. By locating the lock-off in close proximity to the primary orifice, residual fuel is minimized allowing near instantaneous fuel shut-off via selectively de-energizing the lock-off coil (key switch). This prevents backfire in high duty cycle, hot engine applications after the key is turned off. The primary diaphragm and primary chamber housing cover is secured to this base to define a primary fuel chamber. A primary fuel orifice seat is carried by the base, as is a primary control lever that is coupled to the primary diaphragm and primary spring for control of fuel flow through the primary orifice as a function of inlet fuel pressure, temperature dependent fuel vaporization pressure and engine demand. A secondary diaphragm is also secured between the base and secondary cover to define a secondary fuel chamber. A secondary orifice is carried by the primary cover between the primary and secondary chambers, and a secondary lever is coupled to the secondary diaphragm and secondary spring for controlling flow of fuel through the secondary orifice as a function of engine demand. A heat exchange section in the body receives engine coolant or engine oil for heat exchange with fuel so as to heat and vaporize the fuel between the primary and secondary chambers. For air-cooled engines, the coolant passage can be replaced by fins integral with or of the same material as the body. These fins transfer heat into the body to heat and vaporize the fuel. This alternative configuration can also be used as a vapor only system.